/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.optimize.info;

import proguard.classfile.*;
import proguard.classfile.attribute.CodeAttribute;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.SimplifiedVisitor;
import proguard.classfile.visitor.MemberVisitor;

/**
 * This InstructionVisitor marks all fields that are write-only.
 *
 * @author Eric Lafortune
 */
public class ReadWriteFieldMarker extends SimplifiedVisitor
    implements InstructionVisitor, ConstantVisitor, MemberVisitor {
    // *
    private static final boolean DEBUG = false;
    /*/
    private static       boolean DEBUG = System.getProperty("rwfm") != null;
    //*/

    private final MutableBoolean repeatTrigger;

    // Parameters for the visitor methods.
    // We'll set them to true by default, in case this class is being used
    // as a field visitor.
    private boolean reading = true;
    private boolean writing = true;

    /**
     * Creates a new ReadWriteFieldMarker.
     */
    public ReadWriteFieldMarker(MutableBoolean repeatTrigger) {
        this.repeatTrigger = repeatTrigger;
    }

    // Implementations for InstructionVisitor.

    public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        Instruction instruction) {}

    public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        ConstantInstruction constantInstruction) {
        byte opcode = constantInstruction.opcode;

        // Check for instructions that involve fields.
        switch (opcode) {
            case InstructionConstants.OP_LDC:
            case InstructionConstants.OP_LDC_W:
                // Mark the field, if any, as being read from and written to.
                reading = true;
                writing = true;
                clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
                break;

            case InstructionConstants.OP_GETSTATIC:
            case InstructionConstants.OP_GETFIELD:
                // Mark the field as being read from.
                reading = true;
                writing = false;
                clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
                break;

            case InstructionConstants.OP_PUTSTATIC:
            case InstructionConstants.OP_PUTFIELD:
                // Mark the field as being written to.
                reading = false;
                writing = true;
                clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
                break;
        }
    }

    // Implementations for ConstantVisitor.

    public void visitAnyConstant(Clazz clazz, Constant constant) {}

    public void visitStringConstant(Clazz clazz, StringConstant stringConstant) {
        // Mark the referenced field, if any.
        stringConstant.referencedMemberAccept(this);
    }

    public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant) {
        // Mark the referenced field.
        fieldrefConstant.referencedMemberAccept(this);
    }

    // Implementations for MemberVisitor.

    public void visitAnyMember(Clazz Clazz, Member member) {}

    public void visitProgramField(ProgramClass programClass, ProgramField programField) {
        // Mark the field if it is being read from.
        if (reading) {
            markAsRead(programField);
        }

        // Mark the field if it is being written to.
        if (writing) {
            markAsWritten(programField);
        }
    }

    // Small utility methods.

    private void markAsRead(Field field) {
        FieldOptimizationInfo fieldOptimizationInfo = FieldOptimizationInfo.getFieldOptimizationInfo(field);

        if (!fieldOptimizationInfo.isRead() && fieldOptimizationInfo instanceof ProgramFieldOptimizationInfo) {
            ((ProgramFieldOptimizationInfo)fieldOptimizationInfo).setRead();

            repeatTrigger.set();
        }
    }

    public static boolean isRead(Field field) {
        return FieldOptimizationInfo.getFieldOptimizationInfo(field).isRead();
    }

    private void markAsWritten(Field field) {
        FieldOptimizationInfo fieldOptimizationInfo = FieldOptimizationInfo.getFieldOptimizationInfo(field);

        if (!fieldOptimizationInfo.isWritten() && fieldOptimizationInfo instanceof ProgramFieldOptimizationInfo) {
            ((ProgramFieldOptimizationInfo)fieldOptimizationInfo).setWritten();

            repeatTrigger.set();
        }
    }

    public static boolean isWritten(Field field) {
        return FieldOptimizationInfo.getFieldOptimizationInfo(field).isWritten();
    }
}
